Mn is an abundant element required for normal mammalian physiological processes, but both excesses and deficiencies can cause serious health problems. Our recent studies have shown that prepubertal Mn exposure activates the neuroendocrine hypothalamus to stimulate LHRH secretion, an action that generated precocious pubertal development. Thus, this seemingly beneficial effect of Mn to activate the reproductive system may be harmful if an individual is exposed to low, but elevated levels of the metal too early in life. Therefore, the long- term goal of this study is to obtain information which will allow us to better understand the effects and mechanisms of action of manganese (Mn) on the induction of precocious puberty. Molecular and physiological approaches will be utilized to address four specific aims. Aim 1 will assess the effects of prepubertal Mn exposure on the expressions of specific puberty related genes and proteins in the hypothalamus. One of these is KiSS-1, a gene vital for the onset of puberty as it is responsible for the production of the kisspeptins (Kp), which are potent stimulators of hypothalamic luteinizing hormone-releasing hormone (LHRH). Aim 2 will assess upstream actions of Mn on KiSS-1/Kp functions and evaluate its effects on potential upper echelon genes suggested as regulators of KiSS-1 gene expression. Aim 3 will use cultured rat hypothalamic astrocytes to assess the effects of Mn on downstream glial to glial communications involved in the pubertal process. Aim 4 will assess the puberty-related effects of Mn in developing female pups exposed to Mn through their mothers during gestation, lactation or both. This aim will enable us to determine which exposure time caused the most significant insult, and discern whether the effects and underlining mechanisms are similar or different compared to pups in the previous aims that were exposed to Mn during postnatal development. Understanding the involvement of Mn in precocious puberty is clearly important as it relates to adolescent health and development. Because Mn affects humans and its actions on puberty are mediated through normal neuroendocrine channels that apply to all mammals, the proposed study should provide information that will translate to research using primates and human epidemiological studies to further investigate the actions of Mn on precocious puberty and its health related effects.